JP2008213374A - Method for manufacturing substrate for inkjet head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a substrate for inkjet heads in which a driver load for inkjet heads is reduced by increasing the sheet resistance of a heating resistor to cope with a problem in the manufacturing of a large number of nozzle heads corresponding to high speed recording. <P>SOLUTION: When TaSiN or TaBN is formed by reactive sputtering as a heating resistor, the target is made by sintering from each powder and has a relative density of 95% or more. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for manufacturing an ink jet substrate having a heating resistor that generates thermal energy for discharging ink onto a substrate.

  The ink jet recording method has been attracting attention in recent years because it is capable of high-speed, high-density, high-accuracy and high-quality recording and is suitable for downsizing of color (US Pat. No. 4,723,129, US Pat. No. 4,740,796).

  As shown in FIG. 1, the head used for this ink jet recording is provided with a plurality of ejection ports 1001 and an electrothermal conversion element 1002 for generating thermal energy used for ejecting ink from now on. Each ink channel 1003 is provided on the substrate 1004. The electrothermal conversion element 1002 mainly includes a heating resistor 1005, an electrode wiring 1006 for supplying power to the heating resistor 1005, and an insulating film 1007 for protecting them. In addition, each ink flow path 1003 aligns the top plate integrally formed with a plurality of flow path walls 1008 with the electrothermal conversion element on the substrate 1004 by means such as image processing. It is formed by joining.

  Each ink flow path 1003 has an end opposite to the ejection port 1001 communicating with a common liquid chamber 1009, and ink supplied from an ink tank (not shown) is stored in the common liquid chamber 1009. The The ink supplied to the common liquid chamber 1009 is guided from here to each ink flow path 1003 and is formed and held in the vicinity of the ejection port 1001. Here, by selectively driving the electrothermal conversion element 1002, the ink on the heat acting surface is rapidly heated using the generated heat energy to cause film boiling, thereby ejecting the ink.

  FIG. 2 is a schematic cross-sectional portion when cut perpendicularly to the substrate surface along the alternate long and short dash line of XX ′ shown in FIG. 1 in order to show the portion corresponding to the ink path of the substrate 2000 for the inkjet recording head. FIG. In FIG. 2, 2001 indicates a silicon substrate, and 2002 indicates a heat storage layer made of a thermal oxide film. 2003 is an interlayer film made of SiO film or SiN film that also serves as heat storage, 2004 is a heating resistance layer, 2005 is a metal wiring such as Al, Al-Si, Al-Cu, and 2006 is a protective layer made of SiO film, SiN film, or the like. Indicates. Reference numeral 2007 denotes a cavitation-resistant film for protecting the protective film 2006 from chemical and physical impact caused by heat generation of the heat generating resistance layer 2004. Reference numeral 2008 denotes a heat acting portion of the heat generating resistor layer 2004.

  Currently, a TaN film or the like is generally used as the heating resistance layer 2004 used in such an ink jet head. The characteristic stability of this TaN film, particularly the resistance change rate during long-term repeated recording, has a strong correlation with the composition of the TaN film. In particular, it is known that a heating resistor composed of tantalum nitride containing TaN 0.8 hex has a low resistance change rate during long-term repeated recording and is excellent in ejection stability (Japanese Patent Laid-Open No. 7-125218).

  On the other hand, various thin-film heating resistors have been proposed for high-speed thermal recording in thermal print heads that perform recording by directly contacting thermal paper or an ink ribbon. For example, as described in JP-A-53-25442, the first element is at least one selected from Ti, Zr, Hf, V, Nb, Ta, W and Mo, The element is N, the third element is Si, the first element is 5 to 40 atomic%, the second element is 30 to 60 atomic%, and the third element is 30 to 60%. Thus, a heating resistor having excellent life characteristics can be obtained even when heat is generated at a high temperature.

At present, a multi-orifice (multi-nozzle) type ink jet recording head in which a plurality of heating resistors are formed on a substrate is mainly used. For example, there are 64 nozzles and 128 nozzles.
U.S. Pat. No. 4,723,129 U.S. Pat. No. 4,740,796 JP 7-125218 A JP-A-53-25442

  As described above, a TaN film has been mainly used as a heating resistance layer used in an ink jet head because of its characteristic stability, particularly resistance change rate during long-term repeated recording. By the way, in recent years, a multi-orifice type ink jet recording head in which a plurality of heating resistors are formed on a substrate tends to be used. The purpose is to increase the number of nozzles by increasing the length of the head and to increase the printing speed.

  When a plurality of heating resistors are to be formed, the following problems occur when driving the head with a heating element having the same resistance value as in the prior art.

  In order to drive a plurality of formed heads, the driving current of the driver increases as the number of nozzles increases. As a result, the load on the driver increases.

  There are two possible means for solving this problem.

  One is a method of dealing with an increase in driving current by using a larger driver capacity. Although this countermeasure is a very simple method, increasing the capacity of the driver will eventually lead to an increase in the driver cost, and ultimately to an increase in the product cost.

  Another countermeasure is to increase the sheet resistance of the heating resistor.

  Consider this method.

  If the power input to the heating resistor is P, P can be expressed by the following equation.

(Think here in DC)
P = IE I: current E: voltage where E = IR R: resistance
You can write P = I * IR.

I = route (P / R)
Since the amount of heat generated by the heating resistor is proportional to the power P, the ejection of the ink jet can be controlled by managing P.

  If P is constant, it can be seen that the current I decreases as the resistance R increases.

  Thus, the current of the driver can be reduced by increasing the sheet resistance of the heating resistor.

  The main object of the present invention is to solve the above-mentioned problems relating to the heat generating resistor of the conventional ink jet recording head, and to reduce the load of the driver for the ink jet head by increasing the sheet resistance of the heat generating resistor. It is an object of the present invention to provide a method for manufacturing an ink jet substrate in which the problems associated with the reduction in the size of dots corresponding to high definition and the increase in the number of nozzles corresponding to high-speed recording have been addressed.

  Another object of the present invention is to provide a method for producing an ink jet substrate that makes it possible to easily obtain a heating resistor that has little fluctuation in resistance value and stable ejection.

As a result of intensive studies to solve the above problems, the present inventors have achieved the object by providing the following manufacturing method. That in forming the heat generating resistor by reactive sputtering a refractory metal using Ta and an alloy target composed of Si or B is a metalloid is, in a mixed gas atmosphere consisting of Ar and N _2, the alloy target A method of manufacturing a substrate for an ink jet head, wherein the powder of the refractory metal and the metalloid is prepared by a sintering method, and the alloy target has a relative density of 95% or more.

  As described above, the heat generating resistor for ink-jet tends to have high resistance due to an increase in the number of nozzles. It has been difficult to increase the sheet resistance of the TaN film heating resistor which has been mainly used so far.

  As a countermeasure against this, as a heating resistor that changes to TaN, it is considered that a high-melting-point metal Ta and a nitride film made of a semimetal such as Si or B can increase the sheet resistance, and as a result, TaSiN and TaBN films generate heat. It has been found that the resistance value hardly changes even after repeated heating of the resistor, and the sheet resistance can be increased.

  Furthermore, when these materials are to be formed by reactive sputtering, a target is prepared from each material powder by sintering, and a relative density of 95% or more is used. It has been found that durability characteristics are improved.

  This may be because the film quality is improved by using a target having a high relative density. In particular, the durability is improved by increasing the film density.

  Japanese Patent Laid-Open No. 11-006060 is known as a conventional technique characterized by increasing the relative density of a sintering target. By the way, the technical field described therein is mainly intended to suppress particles during the formation of a semiconductor electrode film, and is completely different from the present invention in the technical field, effects, and the like. In the present invention, as a result of examining the durability of the heat generating resistor of the ink jet printer in detail, it was found that the durability of the resistor formed with a sintered target having a relative density of 95% or more is improved. is there.

  According to the present invention, it is possible to easily obtain a heating resistor with stable ejection even in the case of a small dot corresponding to high definition of a recorded image and a large number of nozzles corresponding to high speed recording.

  That is, it is possible to provide a substrate for a liquid ejection head that is stably ejected, a liquid ejection head that includes the substrate, and a liquid ejection apparatus that includes the liquid head.

  Furthermore, a low-cost device can be realized by forming a heating resistor having a stable resistance value with little variation.

  Examples of the present invention will be described below. However, the present invention is not limited to the following examples.

In this embodiment, a Si substrate or a Si substrate in which a driving IC has already been formed is used. On this Si substrate, a heat storage layer of 1.2 μm thick SiO ₂ is formed by thermal oxidation, sputtering, CVD, etc., and the Si substrate on which the IC is built is also in the manufacturing process. _Two heat storage layers were formed.

Next, an interlayer insulating film having a film thickness of 1.2 μm made of SiN or SiO ₂ was formed by sputtering, CVD, or the like. Next, a heating resistance layer was formed.

First, using a Ta—Si alloy target, a mixed gas of Ar gas of 80 ccm and N ₂ gas of 10 ccm was introduced from the gas inlet. The substrate temperature at this time was 200 ° C. Then, power was applied to the target, and when the discharge was stabilized, the shutter was opened, and the formation of the heating resistor layer on the substrate was started.

The Ta—Si alloy target used at this time was prepared from Ta and Si materials to a composition of Ta ₆₀ Si ₄₀ (at%) by hot isostatic pressing.
The relative density of this target was 96%.

  After the formation of the heating resistor layer was finished, an Al film having a thickness of 5500 angstroms was formed by sputtering as electrode wiring. Next, a pattern was formed using a photolithographic method to form a 22 μm × 25 μm thermal action part from which the Al film was removed. Next, an insulator having a film thickness of 0.3 μm made of SiN was formed as a protective film by plasma CVD.

  Next, a Ta film having a film thickness of 2300 angstroms was formed as a cavitation-resistant layer by sputtering, and a substrate for an ink jet head as shown in FIG. 1 was prepared by photolithography.

  The durability of the heating resistor was evaluated using the substrate thus prepared.

  First, using this substrate, the ink foaming start voltage Vth was examined. The foaming start voltage Vth is such that the heating resistor has a driving frequency of 15 kHz and a driving pulse width of 1 μsec. Is a voltage at which ink starts to foam while increasing the applied voltage. This foaming start voltage Vth is the same for each head, and if there is little variation, it is preferable because stable ejection is performed regardless of the head. The foaming start voltage Vth of this substrate was about 11V.

  Next, a voltage of 1.3 times the foaming start voltage was applied to this substrate, and a driving frequency of 15 kHz and a driving pulse width of 1 μsec. 1 billion pulses were applied.

  As a result of measuring the change from the initial value of the resistance value after applying the pulse, it was found that the rate of change in resistance was within 3%, and the durability was very excellent.

Ta-Si alloy target was prepared by hot isostatic pressing as a Ta-Si alloy target, and used for an inkjet head in the same manner as in Example 1 except that a material with a relative density of 97% (Ta ₅₀ Si ₅₀ at%) was used. A substrate was prepared.

  Similarly, the Vth of the heating resistor was measured to evaluate the durability.

  The foaming start voltage Vth of this substrate was about 10.8V.

  Next, a voltage of 1.3 times the foaming start voltage was applied to this substrate, and a driving frequency of 15 kHz and a driving pulse width of 1 μsec. 1 billion pulses were applied.

  As a result of measuring the change of the resistance value after the pulse application from the initial stage, it was found that the resistance change rate was within 2.5%, and the durability was very excellent.

Ta-Si alloy target as a Ta-Si alloy target by hot isostatic pressing and using a 96% relative density (Ta ₄₀ Si ₆₀ at%). A substrate was prepared.

  Similarly, the Vth of the heating resistor was measured to evaluate the durability.

  The foaming start voltage Vth of this substrate was about 10.9V.

  Next, a voltage of 1.3 times the foaming start voltage was applied to this substrate, and a driving frequency of 15 kHz and a driving pulse width of 1 μsec. 1 billion pulses were applied.

  As a result of measuring the change of the resistance value after the pulse application from the initial stage, it was found that the resistance change rate was within 2.8%, and the durability was very excellent.

(Comparative Example 1)
A substrate for an ink jet head was prepared in the same manner as in Example 1 except that Ta and Si powders were prepared by hot pressing as a Ta-Si alloy target, and those having a relative density of 81% (Ta ₆₀ Si ₄₀ at%) were used. Created.

  Similarly, the Vth of the heating resistor was measured to evaluate the durability.

  As a result, the foaming start voltage Vth of this substrate was about 10.5V.

  The durability was evaluated in the same manner as in Example 1. As a result, the change in resistance value after applying 1 billion pulses was 8.5%, which was worse than that in Examples 1, 2, and 3.

Ta and B powders are prepared by hot isostatic pressing as Ta-B alloy target, and a relative density of 97% (Ta ₇₀ B ₃₀ at%) is used, and a mixed gas of Ar 60 ccm and N ₂ 15 ccm is introduced. A substrate for an ink jet head was produced in the same manner as in Example 1 except that.

  Similarly, the Vth of the heating resistor was measured in the same manner to evaluate the durability.

  As a result, the foaming start voltage Vth of this substrate was about 12V.

  Further, when the same evaluation as in Example 1 was performed for durability, the change in resistance value after applying 1 billion pulses was 3.5% and the durability was very good.

Ta, B powder as Ta-B alloy target was prepared by hot isostatic pressing, and a relative density of 98% (Ta ₄₀ B ₆₀ at%) was used, and a mixed gas of Ar ₆₀ ccm and N _{2 20} ccm was introduced. A substrate for an ink jet head was produced in the same manner as in Example 1 except that.

  Similarly, the Vth of the heating resistor was measured in the same manner to evaluate the durability.

  As a result, the foaming start voltage Vth of this substrate was about 12.3V.

  Further, when the same evaluation as in Example 1 was performed for durability, the change in resistance value after applying 1 billion pulses was within 3.8%, and the durability was very good.

(Comparative Example 2)
A base for an inkjet head was prepared in the same manner as in Example 1 except that Ta and B powders were produced by hot pressing as a Ta-B alloy target, and those having a relative density of 83% (Ta ₇₀ B ₃₀ at%) were used. Created.

  Similarly, the Vth of the heating resistor was measured to evaluate the durability.

  As a result, the foaming start voltage Vth of this substrate was about 11.9V.

  Further, when the same evaluation as in Example 1 was performed for durability, the change in resistance value after applying 1 billion pulses was 9.2%, which was worse than that in Examples 4 and 5.

It is a schematic plan view which shows the board | substrate of the inkjet head by this invention. It is sectional drawing of a board | substrate when FIG. 1 is cut | disconnected perpendicularly by the dashed-dotted line of X-X '.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1001 Ejection port 1002 Electrothermal conversion element 1003 Ink flow path 1004 Substrate 1005 Heating resistor 1006 Electrode wiring 1007 Insulating film 1008 Channel wall 1009 Common liquid chamber 2000 Base 2001 Silicon substrate 2002 Heat storage layer 2003 Interlayer film 2004 Heating resistance layer 2005 Metal wiring 2006 Protective film 2007 Anti-cavitation film 2008 Thermal action part

Claims (3)

When forming an exothermic resistor by reactive sputtering in a mixed gas atmosphere consisting of Ar and N ₂ using an alloy target consisting of Ta which is a refractory metal and Si or B which is a semimetal, the alloy target is A method for producing a substrate for an ink jet head, wherein a powder of a refractory metal and the metalloid is prepared by a sintering method, and the alloy target has a relative density of 95% or more.   2. The method for producing a substrate for an ink jet head according to claim 1, wherein the alloy target comprising the refractory metal Ta and the semimetal Si or B uses a target produced by a hot isostatic pressure method. The composition range of the alloy target composed of the refractory metal Ta and semimetal Si or B is Ta ₈₀ Si ₂₀ at% to Ta ₃₀ Si ₇₀ at% or Ta ₈₀ B ₂₀ at% to Ta ₃₀ B ₇₀ at%. 2. The method for producing a substrate for an ink jet head according to claim 1, wherein:

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